Solitary herb with a central root, a caudex extensively branching at ground level, and a large number of short vegetative shoots in an often dense tussock. Old, withered leaves are retained for one or often more years. Flowering stems 1–3(5) cm with one pair of reduced stem leaves. Sepals, pedicels, and stems with short, articulate, gland-tipped hairs. For glabrous plants, see comments.
Leaves opposite, 3–6 mm, linear, without distinct sheaths, subacute or acute; lamina with prominent mid vein and two lateral veins (i.e., ‘three-veined’), sometimes also with strengthened margins, veins becoming even more prominent in dry leaves, sometimes with short, articulate, gland-tipped hairs. Dead leaves often persist for several years.
Flowering shoots with a single terminal flower on pedicel 5–15(20) mm.
Flowers radially symmetric with (4)5 free sepals and petals. Sepals 3–5 × 1–1.5 mm, narrowly lanceolate or triangular, acute or acuminate, with three prominent veins, purplish green with narrow, white (hyaline) margin. Petals from shorter than to slightly longer than sepals, 2.5–6 × 1.7–2.0 mm, broadly ovate or obovate, entire, white or rarely pink or pale purple. Stamens 10. Gynoecium of 3(4) carpels with 3 stigmas.
Fruit a one-roomed capsule that opens apically with 3 teeth, with numerous seeds.
Sexual reproduction by seeds; no vegetative reproduction. Flowers small and probably not adapted to insect pollination; self pollination assumed to prevail. The plant flowers and fruits regularly in Svalbard, sometimes twice in one season, and regularly produces large amounts of mature seeds. Seeds germinate to only 7 % in an experiment (Alsos et al. 2013) but we suspect some scarification is needed in this species.
No special adaptation to seed dispersal.
Sabulina rubella can be confused with species of Cherleria and Sagina. It differs from Sagina in having 3 styles and capsule teeth, whereas Sagina has 4–5 styles and capsule teeth. This is not always easily observed, but the shapes of buds, sepals and capsules are usually different. Whereas Sagina has nearly globular buds, short and boat-shaped sepals, and ovoid capsules, Sabulina and Cherleria have elongated buds, lanceolate sepals, and usually more elongated capsules.
Both Sabulina rubella and Cherleria biflora are (mostly) pubescent, whereas Sabulina rossii and S. stricta are (always) glabrous. Sabulina rubella differs from the three others by its three prominent veins in leaves and sepals; the others have at most one prominent vein. The sepals easily differentiate Sabulina rubella from Cherleria biflora; the former has acute to acuminate sepals, the latter obtuse..
Dry sites, on open patches or unstable places, i.e., dry river terraces and gravel bars, exposed ridges, screes. Always on well-drained substrates from loam to gravel, and mostly on ground with a thin snow cover or one of short duration. Largely indifferent as to soil reaction (pH) but more common on circumneutral and basic substrates than on acidic ones.
Common in all zones and sections. Common on Spitsbergen and Nordaustlandet and recorded from Edgeøya, but not from Barentsøya or Bjørnøya.
The general range is circumpolar, arctic–alpine and very wide, in Europe reaching south only to S Norway and Iceland but in the Rocky Mountains reaching far south in the U.S.
Sabulina rubella is a very widespread and quite polymorphic species. The most confusing part of the polymorphy is the existence of glabrous plants and populations. These have been described as a separate species (Arenaria propinqua Richardson) but do not seem to differ from pubescent plants in any other aspects. Such plants are, however, easily mistaken for S. stricta or even for flowering S. rossii. We suspect that some of the reports of S. stricta from Svalbard are based on glabrous S. rubella.
Sabulina rubella has for a long time been accepted as a species of the large genus Minuartia, but Nepokroeff et al. (2001, 2002) found support for Minuartia being heterogeneous and polyphyletic. Dillenberger & Kadereit (2014) divided the species previously assigned to Minuartia on several genera, of which the Svalbard species were assigned to two: Cherleria with C. biflora and Sabulina with S. rossii, S. rubella, and S. stricta.
Alsos, I.G., Müller, E. & Eidesen, P.B. 2013. Germinating seeds or bulbils in 87 of 113 tested Arctic species indicate potential for ex situ seed bank storage. – Polar Biology 36: 819–830. Doi 10.1007/s00300-013-1307-7.
Dillenberger, M.S. & Kadereit, J.W. 2014. Maximum polyphyly: Multiple origins and delimitation with plesiomorphic characters require a new circumscription of Minuartia (Caryophyllaceae). – Taxon 63: 64–88.
Nepokroeff, M. et al. 2001. Origin of the Hawaiian subfam. Alsinoideae and preliminary relationships in Caryophyllaceae inferred from matK and trnL–C–F sequence data. – In: Botanical Society of America. 2001. Botany 2001 Abstracts: 130.
Nepokroeff, M. et al. 2002. Relationships within Caryophyllaceae inferred from molecular sequence data. – In:Botanical Society of America. 2002. Botany 2002 Abstracts: 105.